Recently, ink-jet recording system has been applied in various fields of printing works such as photograph imaging, various types of printings, markings and a specific printing such as a color filter because it enable to form an image easily and with low cost.
Ink-jet ink used for the ink-jet recording includes various types of ink such as an aqueous ink containing water as a principal solvent, an oil-based ink principally containing a non-volatile solvent at room temperature and substantially containing no water, a non-aqueous ink principally containing a solvent volatile at room temperature and substantially containing no water, a hot-melt ink which is solid at room temperature and thermally melted for printing and an active light curable ink capable of curing by active rays such as light, which are selected in accordance with the use.
Besides, a recording medium made from plastics such as polyvinyl chloride and polyethylene is used for outdoor notice board which is required to have a weather resistance for a long period and ability of contacting with a curved surface is used, particularly a medium made from soft polyvinyl chloride is used in wide field of use. The ink-jet recording method is applied as a method suitable for making small amount and diverse kinds of printing matters since plate making is not necessary and the time for finishing is short in such system, though many methods are applied for printing an image on the polyvinyl chloride.
Hitherto, the non-aqueous ink containing cyclohexanone as the principal solvent is used on the occasion of printing on the soil polyvinyl chloride recording medium, for example, an ink-jet ink containing cyclohexanone is disclosed (cf. Patent Document 1). Cyclohexanone has high dissolving ability for soft polyvinyl chloride so that the pigment contained in the ink is come into soft polyvinyl chloride. Therefore, high abrasion resistance and high glossiness of the printed matter can be obtained. However, cyclohexanone is regulated as the First Class Organic Solvent and causes a problem of safety and a local exhaust system is necessary on the occasion of handling the ink-jet ink containing cyclohexanone. Further, organic solvents such as cyclohexanone has potent odor and has issues of long-lasting odor of a printed matter as well as being burden to workers.
In contrast to that, non-aqueous ink containing no cyclohexanone is developed and marketed. For example, non-aqueous inks containing a water soluble organic solvent such as N-methylpyrrolidone and lactone as the solvent capable of dissolving polyvinyl chloride in place of cyclohexanone causing the above problems are disclosed (cf. Patent Documents 2 and 3). Moreover, a non-aqueous ink containing a fixing resin such as a vinyl chloride-vinyl acetate copolymer and an acryl resin for improving the fastness of the image such as abrasion resistance is disclosed (cf. Patent Documents 4 and 5). An ink-jet ink which is inhibited some degree in the odor thereof and has the abrasion resistivity of image formed thereby on polyvinyl chloride medium can be obtained by such constitution.
However in view that a work environment for an user of ink-jet printer is mainly indoor and a printed matter is displayed in harsh environment such as outdoor for a long period, any non-aqueous ink-jet ink is not obtained yet, which has no problem of the safeness and odor and sufficient abrasion resistivity.    Patent Document 1: Japanese translation of PCT international application 2002-526631    Patent Document 2: Unexamined Japanese Patent Application (hereinafter, refers to as JP-A) No. 2005-15672    Patent Document 3: JP-A 2005-60716    Patent Document 4: JP-A 2005-36199    Patent Document 5: WO 2004/007626